It happened. In 1518, People “danced themselves to death” for no obvious reason in Strasbourg, France. One woman started it, and others joined her. Within a month, there were 400 people involved. Many died from pure exhaustion.

If 490 years sounds like a long time to wait for an explanation, it’s hardly a simple case.

In July of 1518, a woman referred to as Frau Troffea stepped into a narrow street in Strasbourg, France and began a fervent dancing vigil that lasted between four and six days. By the end of the week, 34 others had joined her and, within a month, the crowd of dancing, hopping and leaping individuals had swelled to 400.

Authorities prescribed "more dancing" to cure the tormented movers but, by summer's end, dozens in the Alsatian city had died of heart attacks, strokes and sheer exhaustion due to nonstop dancing.

If that sounds weird, Frau Troffea should have been dead through dehydration after three days, max. Six days, and she was already dead, just still dancing, according to theory. That sort of physical exertion isn’t naturally maintainable. Even marathon runners wouldn’t be able to do it.

Some historical corroboration from the profoundly qualified author of a new book doesn’t necessarily help:

Historian John Waller, author of the forthcoming book, "A Time to Dance, A Time to Die: The Extraordinary Story of the Dancing Plague of 1518," studied the illness at length and has solved the mystery.

"That the event took place is undisputed," said Waller, a Michigan State University professor who has also authored a paper on the topic, which has been accepted for publication in the journal Endeavour.

Waller explained that historical records documenting the dancing deaths, such as physician notes, cathedral sermons, local and regional chronicles, and even notes issued by the Strasbourg city council during the height of the boogying rage, all "are unambiguous on the fact that (victims) danced."

"These people were not just trembling, shaking or convulsing; although they were entranced, their arms and legs were moving as if they were purposefully dancing," he said.

Possible reason? Stress-induced psychosis. Having suffered severely from famine, and in many cases wiped out and reduced to begging, the region was in an ongoing crisis. Many had died of starvation. The area was riddled with diseases, including smallpox and syphilis. Waller believes the stress was intolerable, and hence a mass psychological illness resulted.

It was a superstitious time. From the sound of it, these people didn’t have much left in their lives but superstition.

"Anxiety and false fears gripped the region," Waller said.

One of these fears, originating from a Christian church legend, was that if anyone provoked the wrath of Saint Vitus, a Sicilian martyred in 303 A.D., he would send down plagues of compulsive dancing.

Waller’s theory is interesting, and quite a bit more plausible than other theories, including one that it was caused by ergot fungus, the organic version of LSD. Ergot is extremely poisonous, and it’s far more likely to kill people than start an impromptu dance party among starving people.

The fact they were starving, or something like it, makes the dancing even more extraordinary. Where did they get the kilojoules? Perfectly healthy people can be exhausted by a few hours’ dancing, let alone days.

There were many other strange plagues which are pretty good supports for the psychological elements of Waller’s idea, including a “laughing epidemic” that went on for 18 months in Tanzania.

After all, why should social diseases be purely physical?

Just to make the dancing plague a bit more bizarre, there were at least seven other cases of it in the same region during the medieval period, and one in Madagascar in 1840.

They’ve even come up with a few ideas for therapy:

According to medical epidemiologist Timothy Jones, an assistant clinical professor of preventative medicine at the Vanderbilt University School of Medicine, who also reported an incident of hysteria in Belgium following soft-drink consumption, "Outbreaks of psychogenic illness are likely to be more common than is currently appreciated, and many go unrecognized."

Jones recommends that physicians treating such problems "attempt to separate persons with illness associated with the outbreak," conduct tests to rule out other causes, monitor and provide oxygen for hyperventilation, attempt to minimize the individual's anxiety, notify public health authorities and seek to assure patients that, while their symptoms "are real…rumors and reports of suspected causes are not equivalent to confirmed results."

Perhaps Dr. Jones would like to take a look at the American financial sector, where a sort of fiscal disco has been having much the same effect as the dancing plague of 1518... just more expensive...